Biology Aqa Topic 8 PMT (A+ Graded)

What is a mutation? correct answers An alteration to the DNA base sequence. Often arise spontaneously during DNA replication. What are addition and deletion mutations? correct answers Where one or more nucleotides (bases) are either inserted or deleted from the DNA sequence. What is a substitution mutation? correct answers Where one nucleotide (base) in the DNA sequence is replaced by another. What is a duplication mutation? correct answers Where one or more nucleotides (bases) duplicate and repeat. What is an inversion mutation? correct answers Where a group of nucleotides (bases) become separated from the DNA sequence, then rejoin in the reverse order i.e. they have flipped. What is a translocation mutation? correct answers Where a group of nucleotides (bases) become separated from the DNA sequence, and are then inserted into the DNA of a different chromosome. Which mutations are most likely to have a significant impact and why? correct answers Insertion, deletion, duplication, translocation. Because they produce a frameshift, meaning the entire amino acid sequence produced will be different. Which mutations are most likely to have a smaller impact and why? correct answers Substitution, inversion. Because they only alter one or very few triplets, the amino acid sequence might not be affected due to the degenerate nature of the genetic code. Is a mutation resulting in a change to the amino acid sequence always harmful? correct answers No may be neutral if the resulting change in protein has no effect on the organism. Also may be beneficial, which is the basis for evolution and natural selection. correct answers What is a mutagenic agent? Give examples of this. correct answers Factors that increase the rate of gene mutation. Chemical mutagens such as alcohol and benzene. Ionising radiation such as UV and x-ray. 8.2 What is a stem cell? correct answers Undifferentiated cells, that can divide indefinitely and turn into other specific cell types.